Nested interrupts problem, not SA_INTERRUPT

Richard Black (Richard.Black@cl.cam.ac.uk)
Wed, 12 Jul 1995 14:04:55 +0100

I posted this on comp.os.linux.development.system but havn't had a response.

I have written a device driver which is using an interrupt (5 actually). I am
not using the SA_INTERRUPT flag. However when my interface is generating a very
heavy interrupt load I observe the system clock falling behind wall clock time.

My reading of the code in irq.c and irq.h is that with no flags it should be
possible for the clock interrupt handler to interrupt my devices handler
preventing this slippage.

I have checked the interrupt enable flag when inside my device driver and it
does appear to be set.

Can anyone shed any light on this please?

In case its relevant this is slackware 2.3.0 linux 1.2.8 HP Vectra 386/33U,
/proc/interrupts shows:
0: 866007 timer
1: 2 keyboard
2: 0 + cascade
5: 42555849 EATM Interface
10: 115080 3c509
13: 1 math error
14: 15300 + ide0

Thanks,

-----
Richard Black (usual disclaimers)
University of Cambridge
Computer Laboratory
Cambridge
United Kingdom